1. Field of the Invention
The present invention relates to an improved optical filter capable of efficiently preventing reflection of the light between an optical filter such as a color filter substrate and a color converting substrate, and a light emitting part in various kinds of displays such as an organic electroluminescent (EL) display, in particular, capable of improving the light incident efficiency to the optical filter, and a display comprising the same, in particular, an organic EL display.
2. Description of the Related Art
The organic EL element, in principle, has a structure with an organic EL light emitting layer interposed in between an anode and a cathode. For providing an organic EL display capable of providing the color display using an organic EL element practically, there are (1) a method of arranging organic EL elements each emitting the three primary colors, (2) a method of combining an organic EL element for emitting a white light and a color filter layers of the three primary colors, and (3) a CCM method of combining an organic EL element for emitting a blue light and a color converting layer (CCM layer) for the color conversion from blue to green, and from blue to red, or the like.
In particular, in the (3) CCM method, since only one kind of the organic EL element to emit the same color is needed, there is no need of providing the organic EL elements of each color in an uniform property, as in the organic EL display of the method (1). Moreover, the disadvantage of the low white light utilization ratio when decomposing the color with color filters of the three primary colors, as in the organic EL display of the method (2), is solved so that the luminance of the display can be improved by heightening the conversion efficiency of the CCM layer, and thus it attracts the attention.
In the case of the method (2), a part of the output light form the organic EL element is reflected when being incident into the color filter layer in the display. And in the case of the method (3), in the display, a part of the output light from the organic EL element is reflected when being incident into the color conversion layer. Moreover, also in the case of the method (1), since a color filter layer is generally accompanied, apart of the output light from the organic EL element is reflected when being incident into the color filter layer in the display. These reflections lower the incident efficiency of the light into the color filter layer, or the incident efficiency of the light into the cover conversion layer.
For eliminating the reflection on the surface of the color filter layer or on the surface of the color conversion layer in the display, (a) roughing of the surface, (b) providing a reflection preventing layer comprising plural layers of different refractive indices, or the like can be considered. However, if a layer containing fine particles is laminated by coating or the like, for the purpose of (a) roughing, since a part of the light is lost due to the irregular reflection of the incident light, the incident efficiency from the display into the color filter layer or the color conversion layer is lowered. Moreover, management of the paint for obtaining a certain roughened surface is difficult. In the case of (b), plural layers should be laminated so that the number of processes for preventing the reflection is increased.
The applicant has proposed a reflection preventing film comprising a transparent layer made of a cured product of an ionizing radiation curing type resin composition, having a concave-convex part with an endless number of minute concave-convex formed on a transparent base material film by a pitch of the wavelength of the light or less. And furthermore, the applicant has proposed the prevention of the reflection of the external light by laminating or disposing a reflection preventing film on the surface of various kinds of displays (for example, Japanese Patent Application Laid-Open (JP-A) No. 2001-264520 (see page 3, FIG. 1)).
However, according to the above JP-A No. 2001-264520 (page 3, FIG. 1), the reflection preventing film is intended to apply on the surface of the display, that is, the part where image light from the display is finally output. The prevention of the reflection of the light deriving from the external light, that is, the interior illumination, or the like is intended in the reference, but not the reflection of the image light, and thus the incident efficiency of the light from the display into the surface of the color filter layer or into the color conversion layer is not intended.